tracing: fix datasource adaptation in perfetto config

This CL fixes a bug in AdaptPerfettoConfigForChrome() in
crrev.com/c/5581575 - |enable_system_backend| needs to be propagated
so that only Chrome data sources are adapted in system background tracing scenarios.

Bug: b:388424720
Test: unit test AdaptPerfettoConfigForChromeTest.EnableSystemBackend*
Change-Id: Ie74b20c719854682f29401d614fb68e5e4135113
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6275227
Reviewed-by: Mikhail Khokhlov <khokhlov@google.com>
Reviewed-by: Etienne Pierre-Doray <etiennep@chromium.org>
Commit-Queue: Chinglin Yu <chinglinyu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1422622}

services/tracing/public/cpp/perfetto/perfetto_config.cc

@@ -414,7 +414,7 @@ bool AdaptPerfettoConfigForChrome(
   for (auto& data_source_config : *perfetto_config->mutable_data_sources()) {
     AdaptDataSourceConfig(data_source_config.mutable_config(),
                           chrome_config_string, privacy_filtering_enabled,
-                          client_priority);
+                          client_priority, enable_system_backend);
   }
   return true;
 }

services/tracing/public/cpp/perfetto/perfetto_config_unittest.cc

@@ -234,4 +234,52 @@ TEST_F(AdaptPerfettoConfigForChromeTest, Systrace) {
 }
 #endif  // BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_CASTOS)
 
+TEST_F(AdaptPerfettoConfigForChromeTest, EnableSystemBackend_NonChrome) {
+  auto perfetto_config = ParsePerfettoConfigFromText(R"pb(
+    data_sources: { config: { name: "linux.some_system_ds" } }
+    data_sources: { config: { name: "linux.ftrace" } }
+  )pb");
+
+  EXPECT_TRUE(AdaptPerfettoConfigForChrome(
+      &perfetto_config, false, false,
+      perfetto::protos::gen::ChromeConfig::USER_INITIATED, true));
+
+  // System data sources are not adapted.
+  for (auto& ds : perfetto_config.data_sources()) {
+    EXPECT_FALSE(ds.config().has_chrome_config());
+  }
+}
+
+TEST_F(AdaptPerfettoConfigForChromeTest, EnableSystemBackend_Chrome) {
+  auto perfetto_config = ParsePerfettoConfigFromText(R"pb(
+    data_sources: {
+      config: {
+        name: "org.chromium.trace_event"
+        track_event_config: {
+          enabled_categories: [ "foo", "__metadata" ]
+          disabled_categories: [ "*" ]
+        }
+      }
+    }
+    data_sources: {
+      config: {
+        name: "track_event"
+        track_event_config: {
+          enabled_categories: [ "foo", "__metadata" ]
+          disabled_categories: [ "*" ]
+        }
+      }
+    }
+    data_sources: { config: { name: "org.chromium.trace_metadata" } }
+  )pb");
+
+  EXPECT_TRUE(AdaptPerfettoConfigForChrome(
+      &perfetto_config, false, false,
+      perfetto::protos::gen::ChromeConfig::USER_INITIATED, true));
+
+  for (auto& ds : perfetto_config.data_sources()) {
+    EXPECT_TRUE(ds.config().has_chrome_config());
+  }
+}
+
 }  // namespace tracing